What is a ruler for each piece of wood?

(Zhou Changxiang)

In order to obtain the stand data, the DBH of each tree was measured and registered in a certain range. Also known as tree-by-tree investigation. This is the most basic method to measure forest volume. Each wood shall be measured according to the diameter step. The size of the diameter step used is usually determined by the average diameter of the stumps. The average diameter of the stand is less than 6 cm, and the diameter step of 1 cm is adopted; 6 ~ 12 cm adopts 2 cm diameter steps; For 12 cm or more, a diameter step of 4 cm shall be adopted. When 1 cm and 2 cm diameter step are adopted, the initial diameter step is generally 6 cm; When a diameter step of 4 cm is adopted, the initial diameter step is 8 cm. Trees below the initial diameter step are counted as young trees, and the ruler is not checked. In mixed forests of different ages, tree species and generations should be determined separately. In the investigation of mature forests, trees should be divided into timber forests, semi-timber forests and fuelwood forests according to their external forms (bending, double tops, etc.). ) and internal (decay, etc. ) defects, so as to calculate the stand yield and determine the harvest grade. In order to ensure the accuracy of the ruler, it is required that: ① the observer should be close to the trunk, his hands should be level with the wheel ruler, and the ruler height should be kept at1.3m off the ground; (2) The measurement of slope should be based on the uphill ground of the tree; (3) When the chest height is abnormal, it is necessary to measure it up and down and take its average value; (4) When the branches of trees are below 1.3 meters, they should be measured as two trees; ⑤ The tested trees should be marked; ⑥ The recorder shall report the test data to the ruler. For the convenience of counting the number of plants, the number of plants can be recorded by "positive" or "cause" method to indicate that there are 5 plants or 10 plants. After measuring each tree, the height of the tree should be measured by the diameter step. Generally, 3 strains were measured at the central diameter step, and 1 ~ 2 strains were measured at the upper and lower diameter steps. For height measuring trees, the measured values of DBH and tree height should be recorded accordingly, and the tree height curve should be drawn. Finally, the cumulative quantity is calculated.